Led Vu Meter LM3915

Good afternoon, dear viewers and readers. Today I will tell you about the LED volume unit meter, built on the basis of the integrated circuit LM3915.

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You can find all the necessary information for repeating this device by clicking on the link to Patreon:

• https://www.patreon.com/HOBBYHOMEELECTRONICS

LED VU Meter Kit on Tindie:

• http://tiny.cc/ls47tz

Links to radio components:

Radio parts store:

• http://ali.pub/3a5caa

Multi-colored LEDs:

• http://alii.pub/6968td

Microchip LM3915:

• http://ali.pub/4o1ruy

Microchip NE5532:

• http://ali.pub/4o1sap

DC power connector:

• http://ali.pub/4ajcc0

DIP switches:

• http://ali.pub/4o1tup

Header & Socket connectors 2.54 mm:

• http://ali.pub/4o1ukk

Mounting plastic racks:

• http://ali.pub/4o1v6x

Tantalum Capacitor 22 uF uF 16 V:

• http://ali.pub/4o1wo0

Capacitor 105J uF 100V:

• http://alii.pub/696924

Power Supply 220V 1A:

• http://ali.pub/4o1x4j

The LM3915 block diagram consists of ten comparators, on the inverse inputs of which an input signal is applied through a buffer operational amplifier, and direct inputs are connected to the taps of the resistive voltage divider.

The outputs of the comparators are sink current generators, which allows you to connect LEDs without using limiting resistors. Indication can be made either by one LED (point mode), or by a line of luminous LEDs, the height of which is proportional to the level of the input signal (line mode).

The input signal will come from a microphone amplifier, assembled on a low-noise operational amplifier NE5532, at the input of the LM3915 microcircuit chip.

The circuit contains two stages with controlled gain. The gain of the first stage is continuously adjustable by a potentiometer in the range of 1 ... 10 times. The gain of the second stage can be changed in steps using a jumper. If the jumper leads are not shorted together, the gain will be greatest, which is determined by the ratio of R8 and R5 resistors. When a jumper is connected to R6 or R7 in parallel with R8, the gain will be less.

On the EasyEDA website, one common circuit was designed out of two circuit diagrams and converted into a double-sided printed circuit board.

A separate circuit diagram and a printed circuit board were designed for the LEDs.

There are two LEDs connected in series at each indication level.

In KOMPAS 3D I created a model in the form of a tower of identical rectangular parts. I will use 5 mm thick organic glass as rectangular parts to improve the light scattering of LED indicators.

Let’s proceed to the installation of the radio components on the control circuit board.

Next, we proceed to the installation of the printed circuit board and the LED linear.

With the help soldering, connect the control circuit board and the LED circuit board together.

Soldering of joints is done both on the outside and on the inside.

Next, we proceed to the assembly of the tower from rectangular parts and organic transparent glass.

For mounting and additional rigidity of the rectangular parts of the tower I will use two m4 studs.

Plastic bushings of 5 mm height are installed for the distance between the parts.

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